The effect of emotion regulation on emotional eating among undergraduate students in China: The chain mediating role of impulsivity and depressive symptoms

This study aimed to examine the relationship between difficulties in emotion regulation and emotional eating and the role of impulsivity and depressive symptoms in mediating this chain. Four hundred ninety-four undergraduate students participated in the study. A self-designed questionnaire was used in the survey from February 6 to 13, 2022, to finish our purpose, including the Emotional Eating Scale (EES-R), Depression Scale (CES-D), Short Version of the Impulsivity Behavior Scale (UPPS-P) and Difficulties in Emotion Regulation Scale (DERS). The results showed that 1) difficulties in emotion regulation, impulsivity, depressive symptoms, and emotional eating were correlated; 2) impulsivity and depressive symptoms separately mediated the relationship between difficulties in emotion regulation and emotional eating; 3) impulsivity and depressive symptoms played a chain mediating role between difficulties in emotion regulation and emotional eating. The current study provided a better understanding of the psychologically related pathway of emotional eating. The results would be helpful for prevention and intervention of emotional eating among undergraduate students.


Introduction
Eating disorders are characterized by persistent disordered eating behaviors that interfere with daily social and psychological functioning [1]. The global incidence of eating disorders in 2019 was 41.9 million worldwide and caused 6.6 million disability-adjusted life years (DALYs) in that year [2]. Patients with eating disorders described their binge eating behaviors as a result of negative emotions [3]. Emotional eating (EE) is combating negative emotions by engaging in binge eating behaviors [4,5]. The number of people who have EE has continually increased over the past years [6]. EE affects people of all ages, and approximately 20% of people regularly adopt emotional eating behaviors [7]. The researcher found that adults aged 21 to 39 are much more likely to have EE [7]. Ashley's study noted that approximately 10% to 60% of adolescents are emotional eaters [8].
Evidence from a follow-up study showed that EE impels people to overeat and causes weight gain [9]. Notably, EE was particularly related to the preference for sweet and high-fat foods, which can lead to excessive intake of high energy-density foods and promote the occurrence of obesity [10]. Researchers have also paid attention to the relationship between EE and weight loss [11] and found that EE hinders weight loss [12], and a higher level of EE is related to less weight loss over the same period [13,14]. As an abnormal eating behavior, EE is the trigger for gastrointestinal disorders and was found to be a factor causing pharyngeal reflux and acid reflux [6].
Emotion regulation is defined as the ability to cope with negative emotions adaptively [15]. Difficulties in emotion regulation were found among obese adolescents with emotional eating [16], which was proven to be one factor in overeating [17,18]. Poor emotion regulation was related to impulsivity [19] and depression [20], both of which were shown to have a positive connection with emotional eating [21,22]. Impulsivity is recognized as rapid and unplanned reactions to stimulation without thinking about the negative consequences of these reactions [23]. It is a multidimensional construct that involves attentional, behavioral, and cognitive components [24] and has been reported frequently for years [25,26]. Data from a large national sample of the United States population showed that nearly 20% of the participants have impulsivity, especially among younger individuals [27]. Forty percent of children and 58.3% of adults had higher clinically elevated impulsivity, as indicated by the data in 2011 [28].
Depression is an unusually low and unpleasant mood-altering negative emotional state that harms personal life and society [29]. The World Health Organization reports that the global prevalence of depression is as high as 12.8% [30]. College students have more negative emotions due to their high academic pressure, uncertain employment prospects, and other problems [31]. The study elucidated that the prevalence of depressive symptoms among college students is increasing [32]. Approximately 23.8% of first-year university students have depressive symptoms [33], and more than 30% of university students have depression [34].

Emotion regulation and emotional eating
Difficulties in emotion regulation lead to unhealthy eating behaviors [35,36], especially binge eating [37]. The escape model explains that individuals who have difficulties in emotion regulation may erode the usual inhibitions around food and make people willing to escape the negative emotions by breaking their dietary rules and restricting their focus to eating itself [38,39]. Emotion regulation and eating disorders had positive relations, as proven by multiple correlation analysis in Italian university students [40]. Gianini investigated 326 obese and bingeeating adults and found that difficulties in emotion regulation can predict emotional eating [37]. A study among 552 undergraduate students demonstrated that difficulties in emotion regulation contribute greatly to emotional eating [36].

The mediating role of impulsivity
Impulsivity is one of the mental dimensions taking part in emotion regulation [41], which is generally regarded as a consequence of impaired executive functioning. Emotion regulation was negatively associated with impulsivity [19]. Prior work proved that emotion dysregulation was related to impulsive behaviors (r = 0.31, p<0.1) [42]. Multivariable analysis indicated that eating disorders are positively associated with impulsivity in obese people [43]. Emotion-based impulsivity may manifest in the form of binge eating [44]. Although individuals realized the adverse effect of this action, the behaviors had become compulsive to escape negative emotions [45]. A sample containing 121 obese participants with binge eating behaviors was proven to have high impulsivity, with an average score of 31.11 assessed by the UPPS-P Impulsive Behavior Scale [43].

The mediating role of depressive symptoms
Depression was taken as a result of inappropriate emotion regulation [46]. A study conducted among university students indicated that individuals with depression had more difficulties in emotion regulation [47]. The results from random effects analyses indicated that difficulties in emotion regulation were connected with depressive symptoms [48]. Researchers used an emotion-provoking film to increase the negative emotion of participants and showed that difficulties in emotion regulation were related to higher levels of depression symptoms [49]. Braden experimented with adults with overweight or obesity and indicated that eating as a response to depression was most closely related to emotion regulation difficulties [50]. A study conducted in a random sample of 10,000 people in Finland revealed that emotional eating is associated with an increase in depression [51].

The chain mediating role of emotion regulation and emotional eating
Increased impulsivity and negative mood may be amplified by difficulties in emotion regulation among overweight people, which was found in Leehr's experiment using electroencephalography and eye tracking [52]. A study among adolescents aged 13-21 years implied that difficulties with impulse control can result in emotional eating when they have a negative mood [53]. A large cohort of studies conducted on adults revealed that impulsivity, as a distinct personality factor, gives rise to one set of depressive illnesses in adults [23]. A study indicated that patients with major depressive disorder had higher scores on the factors that indicated impulsive reactivity [54]. Previous research on adolescents has suggested that impulsivity is related to rumination, self-blaming, and catastrophes [55]. Impulsivity also leads adolescents to encounter adverse situations, which, in turn, result in depression [56]. Above all, difficulties in emotion regulation issues in emotional eating are also related to impulsivity and negative mood. Meanwhile, depression is a typical negative mood.
Although previous studies have proven the relationship between emotion regulation and emotional eating, no study to date has explored this relationship in undergraduate students. For our first goal, we focused on the status of emotional eating among undergraduate students. Next, we aimed to explore the mechanism of emotional eating and test whether impulsivity and depressive symptoms can mediate the relationship between emotion regulation and emotional eating, which has been neglected by existing studies. Our study would contribute to exploring the psychological factors related to emotional eating and finding effective prevention and interventions by mechanism analysis.
We have the following hypothesis: H1: Difficulties in emotion regulation are positively correlated with emotional eating among Chinese undergraduate students.
H2: Impulsivity plays a mediating role in difficulties in emotion regulation and emotional eating among Chinese undergraduate students.
H3: Depressive symptoms play a mediating role in difficulties in emotion regulation and emotional eating among Chinese undergraduate students.
H4: Impulsivity and depressive symptoms play a chain mediating role in difficulties in emotion regulation and emotional eating among Chinese undergraduate students.

Data source
According to the principle of multivariate statistical analysis, the estimated sample size was 5 times the number of observation indexes [57]. Given that there is a potential 10 percent missing samples, 467 samples were planned to be included. The sample was recruited on social networks, and convenience sampling was used in this study. We made an OR code for the questionnaire by the Wenjuanxing app and distributed it via the WeChat app. The participants scanned the OR code by their smartphones online from February 6 to 13, 2022. Verbal informed consent was obtained from all participants. The participants were undergraduate students during the investigation procedure. The inclusion criteria were ① undergraduate students aged from 18 to 26; ② participation in this research was entirely voluntary; no mental health problems. The exclusion criteria were ① completion of the questionnaire in less than 100 seconds; ② age younger than 18 years or older than 26 years. Research Ethics Committee written approval was obtained from the IRB of Peking University (No. IRB00001052-21150). Verbal informed consent was obtained from all participants. Before conducting the online survey, the participants were informed that involvement was completely voluntary and anonymous. In addition, we introduced the purpose of the study again in the guidelines of each questionnaire and emphasized the confidentiality of the survey.

Measures
Emotional eating. Zhu Hong (2012) revised the Chinese version of the Emotional Eating Scale (EES-R), adding an emotional dimension to the original scale [58]. There are 23 items divided into four dimensions: depression, anxiety, anger and positivity. Responses ranged from 1 to 5, with 1 representing a total lack of these emotions and 5 indicating a high degree of emotion. The higher the score, the higher the desire to eat in a certain mood. The Cronbach's alpha coefficient in this study was 0.935.
Emotion regulation. Gratz developed the difficulties in Emotion Regulation Scale (DERS) and his team in 2004 [59]. The scale is a total of 36 items, which can be divided into six dimensions: difficulty in emotional awareness, difficulty in emotional understanding, difficulty in impulse control, difficulty in goal orientation, difficulty in accepting emotional responses, and difficulty in effectively using regulatory strategies. Each item's responses range from 1 (never) to 4 (always). Item 11 is scored in reverse. The higher the score is, the more serious the emotion regulation difficulty and the lower the emotion regulation ability. In this study, Cronbach's alpha coefficient was 0.934. Impulsivity. The short version of the UPPS-P Impulsive Behavior Scale (UPPS-P) is a 20-point evaluation of five different impulsive personality traits that demonstrate conceptual validity [60]. Responses to questions ranged from 1 (strongly agree) to 4 (strongly disagree), with higher scores indicating stronger negative urgency. In this study, Cronbach's alpha coefficient was 0.834.
Depressive symptoms. The Center for Epidemiological Survey, Depression Scale (CES-D) was developed by Radloff, National Institute of Psychiatry in 1977 [61]. The scale has a total of 20 items, each of which measures one symptom. According to the frequency of symptoms occurring in the last week, each item response ranged from 0 (none or very few) to 3 (disagree strongly), and 4, 8, 12 and 16 were scored in reverse. A score less than or equal to 15 indicates no depressive symptoms, 16-19 is likely to have depressive symptoms, and 20 indicates depression symptoms. The Cronbach's alpha coefficient was 0.884.

Data analysis
All statistical analyses were performed with SPSS 25.0. At the outset of the data analysis, descriptive statistics were used to describe the profile of the sample. The Pearson productmoment correlation coefficient (r) was used in the correlation analysis. The range from -1 to 1 and the values of 0.1, 0.3, and 0.5 represent "small", "medium", and "high" correlations, respectively [62]. In the hierarchical regression analysis, the contribution of all these components to emotional eating was examined by including emotion regulation, impulsivity and depression in the final model. Model 6 of the SPSS process plug-in was used to test the chain mediation model. For the significance test of the regression coefficient, the bootstrapping method with 5,000 repeated samples was selected to obtain a robust [63]. The sample of this study was undergraduate students whose average age was 20.1 ± 1.9 years old. The descriptive statistics are shown in Table 1. The majority of the participants were female (62.8%), while 184 males were included. There were 340 junior-grade students in our study, accounting for 68.8%, and the rest of the participants were senior students (N = 154, 31.2%).

Pearson correlation analysis
There was a significantly correlated relationship among difficulties in emotion regulation, impulsivity, depressive symptoms, and emotional eating. As shown in Table 2, Pearson correlation analyses revealed that there was a medium positive correlation between emotional eating and depressive symptoms (r = 0.363, p<0.01), difficulties in emotion regulation (r = 0.260, p<0.01) and impulsivity (r = 0.382, p<0.01). Impulsivity was found to be moderately positively correlated with depressive symptoms (r = 0.422, p<0.01) and difficulties in emotion

PLOS ONE
The Effect of Emotion Regulation on Emotional Eating:The Mediating Role of Impulsivity and Depressive Symptoms regulation (r = 0.473, p<0.01). The correlation between depressive symptoms and difficulties in emotion regulation was high (r = 0.656, p<0.01). The results showed that there were significant positive correlations between difficulties in emotion regulation, impulsivity and depressive symptoms, supporting hypothesis 1. In addition, age was significantly correlated with depressive symptoms, difficulties in emotion regulation and emotional eating, while BMI was insignificantly correlated with these variables.

Hierarchical regression analysis
As shown in Table 3, there were 4 models in the hierarchical regression analysis. Impulsivity may mediate difficulties in emotion regulation and emotional eating. To verify Hypothesis 1, at the first stage (Model 1), difficulties in emotion regulation were added to the model as an independent variable and significantly predicted emotional eating (β = 0.221, p < 0.001). In the second stage (Model 2), impulsivity was included in the model as a dependent variable, and difficulties in emotion regulation significantly predicted impulsivity (β = 0.445, p < 0.001). In the third stage (Model 3), difficulties in emotion regulation (β = 0.572, p < 0.001) and impulsivity (β = 0.127, p < 0.05) significantly and positively predicted depressive symptoms. In the fourth stage (Model 4), the addition of impulsivity and depressive symptoms to the model as independent variables led to a distinct change in the beta value of

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The Effect of Emotion Regulation on Emotional Eating:The Mediating Role of Impulsivity and Depressive Symptoms difficulties in emotion regulation, and difficulties in emotion regulation no longer made a significant contribution to emotional eating.

Mediation analysis
The PROCESS macro of SPSS was suitable for the analysis of the effects of mediation and for chain mediation models with multiple mediating variables [64]. Therefore, we used Model 6 in the PROCESS macro of SPSS to analyze the chain mediation effect of impulsivity and depressive symptoms between difficulties in emotion regulation and emotional eating. Taking emotion regulation difficulties as the independent variable, emotional eating as the dependent variable, and impulsivity and depressive symptoms as the mediating variables, the chain mediation effect test yielded the results shown in Fig 1 and

Discussion
Although emotional eating has been studied for years, few studies have examined emotional eating among undergraduate students and the specific mechanism between difficulties in emotion regulation and emotional eating. In this study, we discussed the mediating role of impulsivity and depressive symptoms in the relationship between difficulties in emotion regulation and emotional eating among undergraduate students. Stressed the significance of regulating emotions and the importance of impulsivity and depressive symptoms in preventing and intervening in emotional eating.

The status of emotional eating
In our study, the average score of emotional eating among undergraduate students was 61, higher than the score of 52 in Shi's study [65]. The mean BMI of the sample was 21.64, which was consistent with the study conducted in 2021, which showed that nearly 80% of undergraduate students had BMI ranging from 18 to 24 [66]. Our results showed that senior students were more likely to engage in emotional eating. It can be explained that senior students usually face more employment and academic pressure as they are near graduation [67]. The current data indicated that males have a higher level of emotional eating than females, which is contrary to some previous studies [6,68]. It can be explained that women are more concerned with weight control and body shape maintenance [69]. Average monthly income is also a factor that influences emotional eating in our study, and lower income indicates a higher level of emotional eating, which is consistent with a previous report [70]. Hemmingsson's theory emphasized that low income may cause negative mood, which finally induces eating energydense foods to alleviate negative emotions and stress [71]. Burdick proved that lower income is associated with greater impulsivity [72]. People with higher impulsivity are deeply influenced by negative emotions, which appear to be the cause of emotional eating [73].

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The Effect of Emotion Regulation on Emotional Eating:The Mediating Role of Impulsivity and Depressive Symptoms

Difficulties in emotion regulation are positively correlated with emotional eating
Based on our study, difficulties in emotion regulation had a positive predictive effect on emotional eating, which verifies H1. People who have difficulties in emotion regulation are more likely to experience negative emotions [74]. A review reported that people with depression use fewer emotion regulation strategies [75]. People with difficulties in emotion regulation cannot understand the feelings they have, and this lack of emotional clarity makes of the eating disorder [37]. Difficulties in emotion regulation lead to an inability to deal with tasks [50] and to use effective regulatory strategies [59], subsequently increasing the probability of eating as an attempt to escape from adverse emotional states [50]. Under negative circumstances, people choose eating as a strategy because they can feel happy in this way [76]; moreover, eating more calories in the first 5 minutes can make them more positive [77]. Dopamine is a probable explanation; eating increases dopamine release by glutamatergic projection to the ventral tegmental area mediates and N-methyl-D-aspartic acid receptor (NMDA) receptor, which then causes the feeling of pleasure to people [78,79]. Above all, difficulties in emotion regulation result in various physical and mental changes, which lead to emotional eating.

The relationship between difficulties in emotion regulation and emotional eating is mediated by impulsivity
The current study found that impulsivity played a mediating role between difficulties in emotion regulation and emotional eating, which verifies H2. Valente (2017) suggested that emotional eating is an iceberg on top of a three-step ladder and that the hidden base of the iceberg is represented by both emotional dysregulation and the level of impulsivity [80]. Difficulties in emotion regulation, especially impulse control, may decrease dopamine D 2 (DAD 2 ) receptor availability in the striatum and result in lower DA-argic activity, which signifies a tendency toward impulsivity [81]. Bratec (2017) found that difficulties in emotion regulation reduce the influence of the prefrontal cortex on ventral striatal aPE signals after then changing the normal status of the striatum [82]. Individuals who cannot activate striatal circuits appropriately may have impaired self-regulatory control, which contributes to impulsive behaviors [83]. Overeating behavior has been confirmed to have an association with impulsivity [84]. Impulsivity may contribute to overeating in situations of uncontrolled emotion [85]. Thus, difficulties in emotion regulation can induce emotional eating through impulsivity, which indicates that enhancing the ability of emotion regulation and reducing impulsivity can improve the status of emotional eating.

The relationship between difficulties in emotion regulation and emotional eating is mediated by depressive symptoms
The current study found that depressive symptoms played a mediating role between difficulties in emotion regulation and emotional eating, consistent with previous studies [86], which verifies H3. Martin et al proved that difficulties in emotion regulation may be a predictor of depression in general adults [87]. Difficulties in emotion regulation lead to added negative moods and might result in depressive symptoms after some time [88,89]. Longitudinal research has found that eating can be a way to temporarily numb uncomfortable emotions, such as depression. Individuals who are experiencing depression may use food as entertainment [90]. Eating triggered by depression was closely associated with emotion regulation difficulties [50]. It is possible that when experiencing negative emotions (e.g., depression), individuals increase their eating behavior as a strategy for regulation. The 5-hydroxytryptamine transporter (5-HTTLPR) has been proven to be associated with depression [91]. Additionally, a study proved that adolescents with depressive symptoms showed a greater increase in emotional eating if they carried the 5-HTTLPR genotype [92]. Thus, methods to boost mood and reduce depressive symptoms can help improve emotional eating.

Impulsivity and depressive symptoms are chain mediators in the relationship between difficulties in emotion regulation and emotional eating
Our results showed the chain mediation of difficulties in emotion regulation on emotional eating through impulsivity and depressive symptoms, which verifies H4. The results of our research are consistent with a previous study, which proved that impulsivity can predict the onset of depression as a distinct personality factor in adults by a logistic regression model [56]. Individuals who have difficulties in emotion regulation are at significant risk of using inappropriate strategies to cope with life events [93]. Past research found that the higher emotion dysregulation group scored significantly higher on impulsivity [94]. Low levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) were found in people classified as impulsive [95][96][97], and levels of 5-HT and 5-HIAA have a positive relationship with the severity of depression and could be good markers for evaluating depression [98]. Our results suggested that difficulties in emotion regulation may have a tendency toward impulsivity and depression. By effectively acting as mediators through impulsivity and depressive symptoms, people might have emotional eating when they have difficulties in emotion regulation [99]. The current study is the first to document a sequential process in which difficulties in emotion regulation affect impulsivity, which in turn predicts depression and thus overeating.

Conclusion
Through our study, it can be seen that the state of emotional eating among Chinese university students is grim. The status of emotional eating seems to be associated with difficulties in emotion regulation. It is time to explore the relationship because emotional eating can increase the risk of obesity and other diseases. The relationship between difficulties in emotion regulation and emotional eating is mediated by impulsivity and depression symptoms, respectively. In addition, impulsivity and depressive symptoms are chain mediators in the relationship between the two.

Strengths and limitations
Our study contributes to understanding the latest situation of emotional eating among undergraduate students. This is the first study to build a chain mediation model that explores the relevant factors and mechanisms of emotional eating. One limitation of the study is that the results cannot be generalized to the overall population because undergraduate students differ in social pressure and the environment from others. The sample was underrepresented to demonstrate the overall situation of college students in China because the sample size is limited and sample sources cannot cover all regions of China. Emotional eating, difficulties in emotion regulation, impulsivity and depressive symptoms were measured by self-report, and the results are not as accurate as laboratory studies or observational measures in daily routine. We cannot make sure that each participant understands the question well and if they wrote a wrong answer that was different from reality. The participants may have false memories or lie to us.
A laboratory study or observational measure is needed to assess emotional eating, difficulties in emotion regulation, impulsivity and depressive symptoms to further explore this research question. Future studies should investigate different results of emotional eating after intervening in the two mediation variables in the current study to explore the impact of emotional eating.